Background and aims: Internet addiction (IA) has been identified as a major public health problem that is more prominent in adolescents and young adults. Some researchers have indicated certain advantages of family-based therapy over other treatments in participants with IA, but no conclusive evaluation has been reported. The present meta-analysis aims to review the efficacy of family-based therapy on Internet addiction in adolescents and young adults. Methods: Relevant articles published from 1996 to February 15th, 2024, were searched from 14 databases, including three Chinese databases. A total of 19,590 articles were identified using a combination of three sets of search terms (Internet addiction, family therapy, and adolescents). Only RCTs and nonrandomized controlled trials were included. Results: 18 studies, most of which were conducted in Asian countries, were included in the final data analysis. The overall severity of Internet addiction in the family-based therapy group was significantly lower than that in the control group. However, significant heterogeneity was detected. Subgroup analysis showed a beneficial effect of family-based therapy when compared with non-intervention and when added to another psychological or behavioural therapy in psychiatric patients with co-medication. Few studies have examined secondary outcomes or follow-up effects. Discussion and Conclusions: Family-based therapy is most effective in reducing the severity of Internet addiction when combined with other therapies, especially medication treatments in psychiatric patients. It might also be helpful to relieve depression and enhance family functions, which needs further evidence. More studies following up on the post-intervention effects are recommended in the future.